Unknown assailants blew up an Egyptian pipeline in Sinai that supplies Israel and Jordan with gas, security sources and witnesses said on Tuesday.

A witness told investigators he saw three men jump out of a small truck at a pumping station in an area known as al-Maidan, southwest of the city of el-Arish, and open fire on the pipeline, the security sources said.

This was followed by a large explosion heard across the city and witnesses said 15-meter high flames could be seen shooting up from the pipeline.

A local hospital said one man was admitted with burns from the blast, which also set olive groves and shacks in the area on fire. Fire brigades were getting the flames under control after the company operating the pipeline cut off the gas supply.

The pipeline has been blown up by assailants believed to be opposed to selling Egyptian gas to Israel six times since President Hosni Mubarak was ousted in February

The last attack occurred in July when men with machine guns in a small truck forced guards at a station out and blew it up.

The extent of the damage caused by Tuesday's blast and the effect on gas supplies to Israel and Jordan was not immediately clear.

Egypt has been trying to charge Israel and Jordan more for its gas after complaining that prices fixed during Mubarak's rule were below market rates.

The pipeline is run by Gasco, Egypt's gas transport company which is a subsidiary of the national gas company EGAS.

The Egyptian armed forces launched a security operation in Sinai in August to root out hundreds of suspected militants believed to be behind some of the attacks on the pipeline and police compounds in the peninsula.

Security sources said then that they had captured a group of four Islamist militants as they prepared to blow up the gas pipeline in el-Arish.